A 700 N man stands in the middle of a frozen pond of radius 6.0 m. He is unable to get to the other side because of a lack of friction between his shoes and the ice. To overcome this difficulty, he throws his 1.2 kg physics textbook horizontally toward the north shore at a speed of 6.0 m/s. How long does it take him to reach the south shore?
2007-06-20 13:37:06 · 2 answers · asked by Idaly M 2 in Science & Mathematics ➔ Physics
conservation of momentum
momentum before = momentum after
Initially, he and the books are not moving, he doesn't has any momentum. After he throws the book, the momentum of the book and his momentum will add to 0, because momentum is conserved.
0 = m1v + m2v
find the mass of the man
w = mg
700N = m (9.8)
m = 71.43kg
0 = (71.43)v + (1.2)(6)
-7.2 = 71.43v
v = -.1008 m/s
the negative means he moves backward toward South.
The man is in the middle of the pond of radius 6.0m, the radius is the distance he has to cover to get to the other side.
x = vt
6m = (.1008m/s)t
t = 59.52s
2007-06-20 13:46:27 · answer #1 · answered by 7 · 1⤊ 0⤋
Use conservation of momentum M1*V1 = M2*V2, where M1 is the man's mass (1N/g) and V1 his velocity, M2 the books mass (1.2kg) and V2 the book's velocity (6.0m/s). The man's velocity is then
1.2*g/700 * 6.0m/s = 0.10 m/sec
He has to travel 6.0 m at the speed; d = v*t, so t = d / v = 6/.10 = 60 sec
2007-06-20 13:48:25 · answer #2 · answered by gp4rts 7 · 1⤊ 0⤋